How to Trim Curves with the Trim Curve Node in Blender Geometry Nodes

What you’ll learn in this guide

The Trim Curve node in Blender’s Geometry Nodes system lets you specify which section of a curve remains in the output. This guide walks through the node’s inputs and operating modes. It also explains what happens to Bezier and NURBS splines after processing, the limitation with cyclic splines, and a warning about curve normals.

Trim Curve can be used to set up workflows that use only a specific section of a curve in architectural modeling and visualization. For example, you might choose which part of a circulation line or a linear façade element to show. These are examples of architectural uses for the node, not ready-made workflows or guarantees of an automatic result for any particular project type.

Requirements

• You need a Blender installation where you can work with Geometry Nodes. The source documentation lists Trim Curve among the curve operations in Geometry Nodes.

• The sources do not specify a minimum Blender version. We therefore do not state a version requirement here; check the interface and node behavior in the version you use.

• The documentation does not mention compute requirements, an account requirement, or pricing for this node.

• Trim Curve requires curve geometry to process. The Curve input takes the curve component, and the Curve output carries the resulting geometry.

How to work with Trim Curve

1. Choose the curve geometry to trim

First, make sure the Geometry Nodes network contains the curve you want to work on. Trim Curve outputs the section between the spline’s start and end positions. The Curve socket takes the curve component, and the result is available from the Curve output. As you set up this basic connection, keep in mind that the Selection field determines which curves the operation applies to.

Selection is a boolean field input that determines whether trimming is applied to each curve. You can therefore use this input to control the selection result. The source documentation does not prescribe a particular selection formula or ready-made value; how the selection field is generated depends on the Geometry Nodes network you build.

2. Set the trim start

The Start input sets the starting position of the section of the spline that remains in the output. You can express this position in two ways: as a proportion of the spline’s length or as a length measured from the start. The setting selected in the Mode property determines which interpretation is used.

It is important to consider the start and end positions together. When Start is greater than End, the result is a single-point spline at the position sampled by Start. This is one of the first things to check if changing the values produces an unexpectedly shortened result or one that no longer looks like a line.

3. Set the end point

The End input defines where the section of the spline in the output ends. The range between the start and end values determines which part of the curve is preserved. Rather than generating a new curve from scratch, Trim Curve selects a range on the existing spline.

You can pass the resulting curve from the Curve output to the rest of the network. Since the sources for this guide do not describe a specific setup for subsequent nodes, we do not assume a particular output chain or interface path here.

4. Choose Factor or Length mode

The Mode property determines how the end points are calculated:

• Factor: Start and end positions are expressed as proportions of each spline’s length. Input values must be between 0 and 1. This approach is useful for describing a section’s relative position regardless of the spline’s length.

• Length: End points are defined by length measured from the start of the spline. Inputs must be between 0 and the length of the relevant spline. The value here represents a distance along the spline, not a proportion.

Do not confuse the two modes. The same numerical value cannot be assumed to represent the same position in Factor and Length mode: one is a proportion, the other a length. Staying within the documented ranges is also a basic check for getting understandable results from the inputs.

5. Check the spline type and normals

After trimming, Bezier splines remain the same spline type; the node adjusts the end control points and handles as needed to preserve the shape’s continuity. NURBS splines, however, are output as poly splines after trimming. Keep this difference in mind in networks where the curve type matters in later stages.

Trim Curve does not currently support cyclic splines. If your curve contains a closed loop, account for this limitation; the documentation does not specify an alternative method that supports cyclic splines.

Because curve normals are calculated from the final curve, trimming can change their direction when the Minimum twist method is used. This is because the Minimum method considers the entire curve when determining the final normals. According to the documentation, in some cases, storing the original normals with a Capture Attribute node and using them later can help prevent this change. If you need to preserve them, design the network to retain the normal information from before trimming.

Common mistakes

• Using a Factor value as a distance: Factor is a proportion of the spline’s length, and inputs must be between 0 and 1. To specify a position by distance, select Length mode.

• Overlooking the Length value’s limits: Length inputs must be between 0 and the spline’s length. Check the relevant spline and selected mode before using values that do not match the curve’s length.

• Forgetting the order of Start and End: If Start is greater than End, the output is a single point at the Start position rather than a normal range.

• Assuming cyclic splines are supported: The documentation explicitly states that Trim Curve does not support this spline type.

• Assuming the spline type will remain unchanged: Bezier splines remain Bezier, while NURBS splines are converted to poly splines.

• Assuming the normals will stay the same: In some cases, trimming can change the normals when Minimum twist is used. If necessary, consider storing the original normal information.

What does this mean for architectural and visualization workflows?

Trim Curve provides a parametric control point for architects, interior designers, and visualization artists who want to use only a specific section of curve-based geometry. Factor mode can be used when working with proportions, while Length mode is suited to defining a direct distance. This distinction separates, for example, selecting a relative section on splines of different lengths from selecting a section based on a measured distance.

On the other hand, curves in an existing project may be cyclic, or subsequent operations may depend on retaining the NURBS type. In these cases, the node’s limitations can affect design decisions. Since the sources provide no hardware requirements or cross-version compatibility information, we cannot recommend specific hardware or guarantee compatibility with a particular version. Testing in the Blender version you use before incorporating the node into a workflow can be helpful, especially for checking curve type and normal behavior.

Next steps

Start by testing Factor and Length modes separately on a simple curve; observe the resulting curve as you change the Start and End values. Then compare the output types for Bezier and NURBS splines. Finally, if your work involves cyclic splines or Minimum twist normals, verify the result separately in a real network that includes those features. This lets you see the node’s limitations before moving to a production file.

Sources and license

This guide was adapted into Turkish based on the Trim Curve node and Geometry Nodes node list in Blender’s official documentation. The sources used are licensed under CC BY-SA 4.0: the Trim Curve node description and the Geometry Nodes reference page.